Plate type heat exchanger support



Dec. 9, 1952 B. e. NEWHALL PLATE TYPE HEAT EXCHANGER SUPPORT Filed Feb. 24. 1947 5 Sheets-Sheet l 0 l 0 r Q INVENTOR.

B. G. NEWHALL PLATE TYPE HEAT EXCHANGER SUPPORT Dec 9, 1952 5 Sheets-Sheet 2 Filed Feb. 24, 1947 INVENTOR.

Ben-$20202 G; ZVwfzaZl BY 0% UK B. G. NEWHALL PLATE TYPE HEAT EXCHANGER SUPPORT Dec. 9, 1952 5 Sheets-Sheet 3 Filed Feb. 24. 1947 v 1 .m wwm Q x @QQQQW @MWQQMH my}. Q Q Q Q .z QQQ Q Q Q QQQQQQQQQQQ Q QQQQQQ 2E QQQQQQQQQQ QQQQQQQQ Q Q Q I Q QQQ QQQ QQQ @w VQHQ Dec. 9, 1952 B. G. NEWHALL 2,621,028

PLATE TYPE HEAT EXCHANGER SUPPORT Filed Feb. 24, 1947 5 Sheets-Sheet 4 INVENTOR.

Ban-'awzin G. jVzzr/zall fi Y %mwifh Dec. 9, 1952 B. G. NEWHALL 2,621,023

PLATE TYPE HEAT EXCHANGER SUPPORT 5 Sheets-Sheet 5 Filed Feb. 24. 1947 Egg/z I drill/4;! n I zllllllililw 3 INVENT 2 22min aim, ma

Patented Dec. 9,

PLATE TYPE HEAT EXCHANGER SUPPORT Benjamin G. Newhall, LittleFallaNfY; ss-aha to Cherry-Burrell Corporation, Wilmington,"

AnplicationFebruary 24, 1947, Serial No. 730,641

1 Claim.

This inventionrelates to apparatus such, for example, as plate type heatexchangers, filter presses and the like, im whi'cli a-pl'urality of plate-like elements or plate like elementsand spacers or frame-like elements are operatively supported in a press in close side-by side position. More particularly,.this invention relates to the novel improvements in the arrangement and construction of the supporting irramework, the plate-like elements and releasable retainers, whereby the plate-like elements are properly supported in operative position or in position for inspection and cleaning...

This invention is particularly well adapted for use in connection with a plate type of heat exchanger of the class commonly usedin the processing of milk and like products. The preferred embodiment of this invention will, therefore, be described, without however being limited thereto, in connection with the adaptation thereof in a sanitarily designed plate type. heat exchanger of the class commonly used in dairies for the heat treatment of milk and other dairy products.-

Plate type of heat exchangers commercially used in dairies are preferably made-of stainless metals, such as stainless steel, which 'addappreciably to the cost and usefulness of the'devices. Attainment of satisfactory heat exchange efl lf ciency between the heatexchangelmedia requires the use of relatively thin metalin'the plate-like elements as well as the operation-of the device under conditions involving reasonably rapid flow of the heat exchange media and the associated reasonably high pressures within the fiow' pas sages of the heat exchange apparatus.

Sanitary processing of food products requires the frequent inspection and thorough cleaning of the individual plates and other elements of the device, particularly those elements which come in contact with the food being processed to determine the sanitary condition of the apparatus and to determine whether-or not failures have occured in the plates.

It is, therefore, the primary object of this in vention to provide a new-and novel arrangement for a plate type of heat exchanger or the like device; in which the plate-like elements are slidably supported on and disengag'eably secured to the supporting frameworkj in which the individual plate-like elements, when in operative position, are supported upona main support element; in which the individualplate-like ele-" ments may readily be moved from" operative poinspected r cleaned'and wmcntheymay be 2 pivotally supported on a secondary or stabilizing support or slidablysuppbrted' u ona primary support and stabilized upon'a secondary support or stabilizer against excessive tilting whensup ported outof. contactwiththe remaining plates; from which secondary or stabilizing support the plate-like elements may easily be removed for further inspection, cleaning: or replacement; and in which device the platelike elements'may' easily be replaced or reinserted intothe press'and' arranged into operative position. I

Other objects and advantages 'of the present invention will be pointed out andmore' fully described in the following description when read in connection with the accompanying drawings, in which: 7 I

Figure 1 is a side 'elevationofa plate type heat exchanger, embodying the present invention, in which the'plate-like' elements", comprese sion elements, andispacing elements are assembled into the supporting framework in operative position.

Figures 2 and 3 are explanatory'views, 'illustrating the procedure to be' followed in removing plate-like elements from a press or frame for a plate typeheat exchanger embodying the pres ent invention." 7 I Figure 4 is a front elevational view taken along linedt of Figural of the "drawings'of' an improved plate-like element for a plate type heat exchanger, embodying the present invention and one of the variants of a retaining means for the plate-like element, as outlined along line 1-4 of Figure 1.

Figure 5 is a sectional view, taken along the lines 5-5 of Figure of the drawings.

Figure 6 is a perspective view of the plate retaining element', illustrated in connection with Figures 2, 3 and 4 of the drawings.

Figure '7 is a partial side elevation of a platelike element, equippedwith the retaining clip of the type illustrated in Figure tor the drawings when assembled in a supporting frame in such a fashion as 'to be freely pivotabl'e' upon the secondary support member. v

Figure 8 is a perspective view of a modified form of retainer for'a' plate-like'element.

Figure 9 is a partialfperspective view of a portion of the plate-likeelement adapted for use in connection with the'retainer' illustrated in Figure 80f the drawings. a

Figure l0 is a View similar'to Figure 7, illustrating the'u'p'per portion ofja plate or the type showninl*igure 9 of fthe'drawings', mounted on a secondary 'suppo'rtrod by the use" of the re tainer, such as illustrated in Figure 8 of the drawings.

Figure 11 illustrates a further variant of a plate retainer in the form of a hairpin-like spring clip mounted on a secondary support rod.

Figure 12 is a view similar to those illustrated in Figures 7 and of the drawings, and illustrates a partial view of a plate, such as shown in Figure 9 of the drawings, mounted in operative position upon the primary and secondary support rods and secured to the secondary support rods by the hairpin-like clip of the type illustrated in Figure 11 of the drawings.

Figure 13 is a partial side elevation of a further variant of a plate retainer supporting a plate on the secondary support element of the support frame.

Figure 14 is a view taken along the lines I4-I4 of Figure 13 of the drawings.

Figure 15 is a modified form of the retainer illustrated in Figure 13 of the drawings.

Figure 16 illustrates a further variant of a plate retainer mounted on a plate assembly in operative position upon the primary and secondary support rods of the support frame.

Figure 17 is an enlarged partial side elevation of a plate, supported by a retainer of the type illustrated in Figure 16 of the drawings upon the secondary support rod of the frame.

Figure 18 is a sectional view of the line I8--I8 of Figure 16.

Referring to the drawings, in which like elements are identified by like numerals, I0 and II represent the vertical risers or base elements of the plate heat exchanger frame or press, which includes a transverse and horizontally disposed lower supporting and stabilizing rod-like element or support I2 and horizontally disposed upper stabilizing and supporting rod-like element or support I3, all secured together to form a rigid supporting framework for a plate type of heat exchanger.

A suitable number of plate-like elements or plates, generally identified by the numeral I4, are, when in operative position in the manner illustrated in Figure 1 of the drawings, primarily supported and stabilized against lateral motion upon the primary or lower support rod or element I2 in the manner illustrated in Figure 4 of the drawings, and further stabilized against lateral motion in that position by the upper support rod or secondary support element I3. In such operative position the plates I4 are compressed between the adjacent faces of the vertical riser I0 of the framework, the compression element I5 and the header or spacing elements I6. The compression element I5 and spacing elements I6 are slidably supported and stabilized upon the support and stabilizing elements or rods I2 and I3. Each of these rods I2 and I3, in turn, is provided at its free end with a handwheel I1, threaded thereto. Suitable sleeve members I8 are telescoped over the rods I2 and I3. The members I8 extend through appropriate bushings 20 in the front vertical riser II. This assemblage is used to apply compressive force against the compression element I5 and in turn against the assembled plates I4 and spacing elements I6 upon the appropriate rotation of the handwheels II. By the use of the described arrangement, it is possible to maintain the individual movable plates I4, spacing elements I6 and compression element I5 in desired operative relation with respect to one another and to seal the edges of the flow spaces formed between 4 the gasketed plates I4. In a conventional man ner, the left vertical riser I0, compression member I5 and the spacing elements I6 are provided with suitable connections, whereby the various heat exchange media may be introduced into the fiow spaces formed intermediate the adjacent, juxtaposed, gasketed and apertured plates I4 when assembled in the desired operative position in the supporting framework.

Each of the plate-like elements I4 is provided with the opposed set of lower and upper, peripheral support and stabilizer engaging slots 2| and 22, into which are received the corresponding lower and upper support and stabilizing rods I2 and I3, respectively. In the variant of the invention illustrated in Figures 2, 3 and 4 of the drawings, each of the plate-like elements I4 is disengageably secured to the upper support rod I3 by a retainer or securing element, generally identified by the numeral 23. The retainer 23, when in operative position, consists of a flexed, resilient, substantially fiat, spring clip 24, provided at each end with anchor bars or anchor elements 25, complementary to and adapted to engage the opposed anchor bar engaging detents or notches 26 in the side of the slot 22 associated with the upper support rod I3. It is, of course, obvious to those skilled in the art that the anchor bars 25 and detents 26 may readily be modified in various manners, too numerous to illustrate. It is equally obvious that as a matter of convenience the anchor detents 26 are also provided in the walls of the lower slot 2I, so that when the plate I4 is inverted, as is common practice, the retainer 23 may be engaged in the notches 26 of the slot 2I.

Upon an inspection of Figure 4 of the drawings, it will be observed that the plate I4 rests upon and is primarily supported upon the lower or primary support rod or element I2 and stabilized when in such operative position against lateral motion of its lower portion by the engagement with the lateral sides of rod I2. Plate I4 is stabilized against lateral motion of its upper end by engagement with the lateral sides of the stabilizing rod I3. It will also be observed that the rod I3 is not in engagement with the retainer 23 when the plates I4 are thus mounted in operative position. Such engagement is obviously not necessary, in view of the fact that the corresponding or complementary elements, such as gaskets, flow apertures and knobs, of the adjacent compressed, juxtaposed plates are placed in the desired alignment by the manner in which the plates are mounted upon the lower support rod I2 and stabilized by rods I2 and I3.

It will be noted also that the spacing of the anchor bars 25 from the rod I3, when seated in the notches 26, is such that they may not be released or withdrawn from the notches or detents 26, excepting when the plate I4 is raised to approximately its maximum elevation, intermediate the rods I2 and I3, to thereby provide the necessary clearance between the outer periphery of the rod I3 and the walls of the slots 22 and the openings of the notches or detents 26 to permit the withdrawal or release of the anchor bars 25 from the detents 26. This is done by taking up the clearance between the lower portion of the rod I3 and the adjacent portion of the plate at the bottom of slot 22. The relative sizes and proportions of the rod I 3, the spacing of the rod I3 from the portion of the walls of the slot 22 where the notches 26 ffs are located, the size of the anchor bars-25, .the notches 26 and the xconfiguration..,of. the, clip 24 must be so selected .and arranged as to make 1 possible -the said-release or withdrawal of the anchor bars 25 when the rod I3 is seated in the lower portion of the s10t'22.

To remove the plates I4 from the supporting framework of the plate type heat exchanger, as illustrated in Figures 1, 2 and 3' of .thedrawings, itis first necessary to suitably. rotate.the.hand wheel I1 to release the compression upon. the compression element I5, and thereafter .separate the plates I l and the spacin element I6 and the compression element I5 in the manner clearly indicated in Figure 2 of the drawings,.to.a degree sufficient to permit the hereinafter described plate removal operation.

Having thus separated the plates llzand the spacing element I6 and the compression element I5 a sufiicient distance, thepplate. I4 is pivoted transversely with respect to the remaining assembled plates in the manner indicated in the illustration of Figure 2 of the drawings. Such pivoting motion is continued'until the slot 2I in the lower periphery of the plate His-disengaged from the primary support or rod I2. Afterthe rod I2 has thus been cleared from the support engaging elements, such as slot 2 I in the lower portion of the plate I4, the plate! may then be pivoted laterally with respect to the remaining assembled plates upon the upper rod I3 and the retaining element 23 in a manner illustrated in Figure 3 of the drawings. In this laterally pivassists toftii'eme} 3, By jroiitw itga tiumg snativtan motion opposite to thatjust describedandillus- -replacedin the press in such a manner asjto be supported upon the lower" support rod I2 'in the fashion illustrated in Figure 4 of the drawings,

. H Inthe n rmalcle aningand inspecting operavtions, it is necessary only to release the'jcompression upon the plates, as heretofore described, and separate a'platef rom the remaining plates by transverse sliding of the'plate'upo'n the rods I2 and I3. The thus s epar'atedplate will beselfsustainin in that: it is stabilized 'against'lateral motion by the engagement of the'rods I2 and I3 in the slotsf2l and 22f1ajnd is stabilised" against excessive tilting byfthe' engagement'of the retainer 23 with the rodIB. I

In the foregoing portion of this specification,

there-has been set forth description of one of oted position, the pivoted plate I4 is supported by the disengageable retainer 23, which has then been placed in sliding contact with the surface of the upper rod I3 by the slight lowering of the plate M incidental to the described pivoting operation. stabilized by the operator at; any desired angle suitable for further inspection or cleaning of the plate.

To remove one or more plates from the supporting framework orpress, it is necessary only I3 is seated or about to be seated in the lower portion of the upper slot 22, the springclip or retainer 23 may then be flexed sufliciently to enable the removal or disengagement of the anchor bars 25 from the detents 26. When the-plate I4 has been elevated in the manner as just mentioned, the rod I3 will no longer obstruct the disengagement of the anchor bars 25. from the notches 26. When the retainer 23 has been removed from the plate I4, the plate may then be withdrawn from rod I3 until the support en gaging slot 22 has been released entirely from the rod I3, whereupon the plate Ilmaythen be entirely removed from the press or framework.

To replace a plate or the likein the supporting framework, it is necessary only to place the plate in the mentioned laterallytilted position with the rod I3 received into the lowermost portion of the slot 22. After the plate is supported in such a position, the operator then flexes the spring element 24 of the retainerZg and inserts the retainer 23 into the mouth of the slot 22 until the anchor bars 25 are in alignment with the detents 26. Upon the release of the fie rion of the spring 24 while in such a, position, theanchor bars 25 will engageor be seated the detents 26, thereby disengageably securing the plate I4 The laterallypivoted plate may be the preferred variants of applicants invention in a plate retainer for a plate type apparatus.

I FiguresS, 9 and. 10 illustrate a second Variant of applicants invention. In the second variant of applicants invention, a ring like plate "retainer element or washer Z'L WhicH'has been telescoped over theupper rod supportand stabilizing rod I3, is provided with two opposedouter.

peripheral 'ofis et shoulders" 28. The shoulders '28 are adapted to be engaged in overlapping "relationshi by the oppositely positioned peripheral i V flanges 29, prov'ided'onthe edge, of the plate I4 at the junctureof' the mouth of the 'slot 22 and the outer peripheral edge of the plate I4. Flanges 2e, which extend outwardly. and" downwardly from the 'upperedge' of the face 'of'the plate I4, as clearly illustratedinFi'gure 9 of the drawings, are of such proportions with respect to the shoulders 28 of the ring '21 as to permit a reasonable degree of 'hinginginotion sufficient to enable the hereinbefore described transVersepivoting ofthe plates I l, as illustrated in Figures 2 and 3 of the drawings, du'ringfthe removal or replacement operation, in which a plate'is either removed or replaced into' the supporting framework or press. rhetoieranees and. proportions are also such as to permit the freetransv'erse sliding of the plates and to -prevent excessive transverse tilting of' the top of a plate supported upon the lower rod I 2 out of contact with the remaining plates. To insert a plate into a press provided with the retaining rin '21, it is'nec'essary only to move the upper edge of the "plate Iiinto position with respect to the lower support rod I 3, so that the rod l3 is received into the lowermostportion. ofjthe slot 22. 'In this position, the outwardly and downwardly turned flanges 29. may be placed'in overlappin relation with the complementary shoulders 28'of the ringlike plate retainer 21. "When'theflang'es 29 have thus engaged the shoulders 28 ofthe rings.

I 21, the plate may then be laterally and trans-.

versely pivoted into operative position in the:

manner clearly illustrated in Figures 2 and 3:

in Figure 6 of the drawings. Toj'rer'nove aplate from a press provided "with theret'ainer' ring 21,

the opposite procedure is followed.

In Figures 11 and 12 of the drawings, there is.

tion in the form of a, hairpin-like spring clip, also adapted to be used as a retainer for the type of plate illustrated in Figure 9 of the drawings. In this variant of applicant's invention, it is contemplated that the hairpin-like clip, generally in dicated by the numeral 30, will be disengageably clasped or engaged on the rod I3 in such jposition that the flexed arms 31 thereof, generally speaking, will be in a horizontal position :and extending in a gripping contact on either side of the rod I3 a sufficient distance as to overlap the mouth of the slot 22 and in turn to be overlappingly engaged by the outwardly and downwardly turned flanges 29 of the plate I4. By

this arrangement, the plates I4 may be pivotally supported in a hinge-like fashion upon the upper branch I3 of the hairpin-like clip 30 when released from the main support rod I2 and will be stabilized against excessive transverse tilting in =those instances where an individual plate is sup- ;ported independently upon rod I2 out of contact with the remaining rods. To remove a plate =I4 from the supporting framework or press or to replace a plate I4 into the supporting framework or press, when using a variant of applicants invention involving the hairpin-like clip pin 30, illustrated in Figure 11 of the drawings, substantially the same procedure is followed as when using the retainer ring 21, illustrated in Figure 8 of the drawings.

In Figure 12 of the drawings there is illustrated a partial view of a plate I4 of the type partially illustrated in Figure 9 of the drawings, in an assembled, operative position in a supporting press or framework, clearly indicating the manner in which the plate I4 is supported upon the lower rod I2 and stabilized by the combined action of the retainer 30, the rod I3 and the flanges 29 at the upper end of the plate I4.

Figures 13 and 14 illustrate a further modified variant of applicant's invention, also adapted to be used with a plate of the type illustrated in Figure 9 of the drawings, and which is provided with the outwardly and downwardly turned flanges 29. Figure 15 illustrates a modification of the variant of the invention illustrated in Figures 13 and 14. In these variants of the applicants invention, illustrated in Figures 13, 14 and 15 of the drawings, a retainer pin 32 is secured to one or both of the flanges 29 after the plate I4 has been brought into position with respect to the upper supporting rod I3 in such a manner that the support rod I3 has been received into the lower portion of the slot 22. When the plate I4 and the rod I3 have thus been brought into relative position, the pin 32 is placed across the mouth of the slot 22, so as to completely span the same, and to be overlappingly engaged by the outwardly and downwardly turned flanges 29 at the upper edge of the plate I4. When in such position, the pin 32 is then looked to the plate I4 by driving a key pin 33 through suitable openings in the flange or flanges 29 and the pin 32. A modified form of retaining the pin 32 in proper position with respect to the flanges 29 is illustrated in Figure 15 of the drawings, and contemplates that after the pin 32 has been placed in position in the manner illustrated in Figure 13 of the drawings, suitable detents 34, such as may be made by the use of an appropriate punch, are formed in each of the flanges 29 beyond the outer ends of the retainer pin 32, thus locking the pin 32 in position on the plate I4.

The manner of pivoting the plate I4 into and out of operative position in the supporting press when the plate I4 is equipped with a retainer pin 32 is accomplished by following the same procedure as that hereinbefore described for use with the mentioned variants of applicant's invention and as generally illustrated in Figures 2 and 3 of the drawings. To completely remove the plate from the press, when using a retainer pin 32, it will, of course, be necessary to either remove the key pin 33 or to remove the detents 34 and then withdraw the pin 32 from the flanges 29. The transverse stabilization of the upper portion of a plate supported independently upon the rod I2 out of contact with the remaining plates results from the engagement of the pin 32 with the rod I3, whereby excessive tilting of the plate is prevented.

In each of the hereinbefore described variants of the applicants invention, such as the variants contemplating the use of the spring clip retainer 23 or the ring 21 or the hairpin-like retainer 30 or the retainer pin 32, it is contemplated that such retainer, when in operative position, will completely span the mouth of the slot 32 outwardly of the supporting and stabilizing rod I3. It is further contemplated that each plate I4 be individually provided with a retainer element, thereby permitting the transverse and lateral tilting of the individual plates in the operation of inserting plates in the supporting framework or the operation of withdrawing plates from the supporting framework or in the operation of tilting the plates for inspection and cleaning, all in the manner as hereinbefore described, or as diagrammatically illustrated in Figures 2 and 3 of the drawings.

In Figure 17 of the drawings, there is illustrated a further variant of applicants invention. which contemplates the use of the plate I4 of the type illustrated in Figure '7 of the drawings, in which at least the upper slot 22 is provided with opposed notches or detents 26.

After all of the plates I4 have been assembled on the supporting framework or press, with the supporting rods I2 and I3 in the complementary peripheral slots 2I and 22 of the plates I 4, a locking bar 35, provided with outwardly extending flanges 36 at its lower face, is telescoped through the outer openings of the slots 22 of the assembled plates I4 with the flanges 36 of the bar 35 engaging the complementary detents 26 in the wall of the slots 22. By this arrangement, the locking bar 35 will span the outer opening of the slot 22 outwardly of the supporting rod I3. thereby locking the plates I4 in position on the supporting framework which includes the rods I2 and. I3.

It may appear obvious that any appreciable transverse or any lateral tilting of the plates I4, in the manner as diagrammatically illustrated in Figures 2 and 3 of the drawings, will not be possible when using the locking bar 35, illustrated in Figure 17 of the drawings. However, upon a release of the compression upon the compression element I5, the spacing element I6 and the plates I4, the plates I4 may be separated one from another any desired distance as limited by the expanse of the supporting press or framework, so as to enable inspection and cleaning of the plates. When thus separated, any individual plate may be supported in substantially vertical arrangement out of contact with any remaining plates. To remove any plate I4 from the supporting press or to insert any plate I4 into the supporting press when using the retainer bar 35 of the type illustrated in Figure 17 of the drawings, it is necessary first to withdraw the bar 35 from the assembled plates [4, after which the transverse and lateral tilting motion of the plates, as diagrammatically illustrated in Figures 2 and 3 of the drawings, may be utilized either to replace or remove plates into the press or supporting framework.

From the foregoing description of applicants invention it is apparent that applicant has provided a simple, unique and novel means for detachably securing plates or the like to the supporting and stabilizing framework of the plate type apparatus. Plate retainers of this particular nature are of great importance and utility, in that they enable the ready handling, cleaning and inspection of numerous plates in a plate type heat exchanger, without the necessity of entirely removing each individual plate from the supporting framework and press and at the same time avoiding the danger of freed plates dropping from the press, thereby preventing the probable damage to the relatively fragile and gasketed plates.

It will be appreciated by those skilled in the art that in a device embodying the present invention the supporting elements or rods may readily be arranged in a different order with respect to one another. For example, the supporting rods may be arranged in a substantially horizontal plane instead of being arranged horizontally in substantially vertical plane, as illustrated in the various modifications of the preferred embodiment of this invention. Similarly, it will be obvious to those skilled in the art that elements other than rods may readily be used for supporting and stabilizing the plates in the supporting framework or press.

Accordingly, it is desired that this invention should not be limited to the specifically described vertical arrangement of the plate-like elements or the use of supporting rods referred to in the receding description.

Having thus described the illustrated and preierred embodiments of this invention in a plate type apparatus, the invention is not to be restricted to the specifically illustrated embodiment thereof, as set forth in the drawings and as heretofore described, excepting insofar as necessary by the prior art disclosures and by the appended claim.

This invention is hereby claimed as follows:

A device, for example for heat exchange or filtering purposes, of the type in which a number of plate-like elements are held in closely spaced or abutting relation, if desired under compression, upon a pair of support members forming part of a frame which is provided with means for increasing the space available to the plate-like elements on the support members, each element being provided with notches at opposite ends for receiving said support members, characterized by the feature that each plate-like element is carried by one of said support members and is stabilized against lateral displacement by engagement of the other support member with the notch in the associated end of the element, and that a retaining member is disengageably associated with the plate-like element in position to bridge the last mentioned notch, there being a clearance between said retaining member and either the plate-like element or the stabilizing support member to permit movement of the plate-like element in the direction of a line connecting the two notches.

BENJAMIN G. NEWHALL.

REFERENCES SITE!) The following references are of record in the l file of this patent:

UNITED STATES PATENTS Number Name Date 2,141,222 Pioch Dec. 27, 1938 2,252,916 Crosby Aug. 19, 1941 FOREIGN PATENTS Number Country Date 528,221 Great Britain Oct. 24, 1940 543,636 Great Britain Mar. 5, 1942 

